The present invention relates to a data transmission system for connecting a controller with drives in machine tools or production machines via a data bus, and more particularly for connecting a controller with differently configured drives or for connecting differently configured drives with each other using different bus systems. In the application, the term “production machine” is used here in a generic sense and includes also robots which generally follow the concepts outlined here.
Currently two different commercially available control topologies are used for controlling motors and/or axles of machine tools or production machines, including robots. One control topology is referred to as a central control topology, whereas the other control topology is referred to as a drive-based control topology.
FIG. 1 shows in the form of a block diagram an exemplary conventional central control topology. This control topology includes a controller 1 which forms a self-contained building block and is connected for data exchange via an external data bus 2 to external drives 3a, 3b and 3c, and optionally to additional drives (not shown for sake of clarity). Each drive 3a, 3b and 3c includes control modules implemented as hardware and/or software modules, as well as a converter module for controlling and powering a motor 5a, 5b or 5c which drives, for example, an axle of the machine tool or production machine. The converter module need not be integrated in the drive, but can also be an external module connected to the drive. The control modules and the converter modules are not shown for sake of clarity.
For determining the actual controlled variables, the individual drives are connected with transducers, whereby only one corresponding transducer 6a, 6b and 6c is shown in FIG. 1 for sake of clarity. In addition, as depicted in FIG. 1, the drives 3a, 3b and 3c are frequently connected with I/O units (input output units) 4a, 4b and 4c to enable exchange of data and/or signals between the drives and the I/O units. The I/O units 4a, 4b and 4c can also be an integral component of the corresponding drive. For controlling a motor of an axle of the machine, the controller 1 transmits via the external data bus 2 a desired axle value (e.g., desired position value or desired rotation speed value) to the external drive 3a which controls the motor 5a according to a preset desired axle position value. With the central control topology, the controller 1 and the external drives form separate units that are connected with each other for data exchange via the external data bus 2 which can be implemented, for example, as a Profibus.
FIG. 2 shows in form of a block diagram a different conventional control topology referred to as drive-based control topology. Unlike the central control topology depicted in FIG. 1, the controller 1 of the drive-based control topology together with an internal drive 8 forms a single unit which is referred to as drive-based controller 7. The controller 1 and the internal drive 8 is connected for data exchange via an internal data bus 12 which can be implemented for example as PCI (Peripheral Component Interconnect) data bus. The internal drive 8 is also connected with an I/O unit 9, a motor 10 and a transducer 11. The drive 8 includes control modules implemented as hardware and/or software modules, as well as converter modules for controlling and powering a motor 10 which drives, for example, an axle of the machine tool or production machine. The converter module need not be integrated in the drive 8, but can also be an external module connected to the drive. A single drive can also include several converter modules. The control modules and the converter modules are not shown in FIG. 2 for sake of clarity. The motor 10 is controlled in the same manner as described above with reference to the central control topology, by transmitting desired values from the controller 1 via the internal data bus 12 to the internal drive 8a as desired controlled variables. Optionally, the drive-based controller 7 can also have several internal drives, as illustrated in FIG. 8.
In the two control topologies described above, the actual values determined by the transducers and I/O units are returned to the controller via the data bus, for example for display to an operator. It should be mentioned that the internal drive 8 can also be connected to several motors, transducers or additional I/O units, so that several axles can be controlled simultaneously using a single internal drive 8.
The drive-based control topologies of FIG. 2 are increasingly used due to their favorable cost and performance. However, disadvantageously, the drive-based control topology can control only a limited number of motors and/or drives when using a single drive-based controller 7. To this date, it has not been possible to expand drive-based control topologies by, for example, connecting external drives to a drive-based controller.
It would therefore be desirable and advantageous to provide an improved system for controlling drives of machine tools and/or production machines that are capable of operating with different drive topologies, which obviates prior art shortcomings and more specifically facilitates porting existing user applications between the different drive topologies.